In modern medical practice, there is extensive use of various types of catheters, instruments, devices and implants for various medical procedures. The medical science is increasingly adopting minimally invasive technologies to address and remedy various pathologies and disease states affecting the human body. One of the advantages of such minimally invasive technologies is that they can be done through smaller keyhole incisions, stab punctures and/or through natural orifices of the body into cavities and vessels in the body. Such methods are intended to mitigate trauma to the body and to expedite patient recovery.
Various medical instruments, devices and implants that are transported into and out of the body through these minimally invasive incisions are typically small in diameter, linear and, consequently, can be difficult to guide and navigate into, through, and out of the body. The medical community has long used guide wires to address the difficulties of exacting the location and placement of medical instruments, devices and implants.
Coring, reaming, cutting and dilation devices, such as drills, reamers, dilators, taps, shears, energy delivery tools and similar instruments, are often guided into a desired position over a guide wire to open or create new passages into the body. Imaging devices such as cameras, scopes, probes and illumination fibers have been known to be placed over guide wires. Implants, such as stents, bone screws, intra-medullar rods, soft tissue anchors, valves and various other implants are commonly placed over guide wires. Commonly, the tubular structures of the body are intervened with devices known as catheters that are placed and delivered over guide wires.
A catheter is typically a hollow flexible tube for insertion into a body cavity, duct, or vessel to allow the passage of fluids or distend a passageway. Catheters thereby allow drainage, injection of fluids, or access by surgical instruments. The process of inserting a catheter is called catheterization. Often, a catheter is a thin, flexible tube (“soft” catheter). A catheter left inside the body, either temporarily or permanently, may be referred to as an indwelling catheter. A permanently inserted catheter may be referred to as a permcath. The three major types of catheters are coronary, renal, and infusion catheters. Other types of catheters exist for broad applications such as drainage, administration of fluids, measurement of pressures, circulation, etc.
Coronary catheters are used for procedures that involve insertion through a blood vessel into the heart for diagnostic and treatment purposes. For example, coronary catheters are commonly used for angiography procedure, which involves taking x-rays of blood vessels after injection of a radiopaque substance. Other common uses of the coronary catheters are angioplasty procedures that involve altering the structure of a vessel, placing stents, deploying valves and performing ultrasound and related diagnostic and treatment imaging studies in the heart or in peripheral veins and arteries.
Renal catheters are typically used for drainage of urine from the bladder through the urethra. A well-known type of renal catheters are Foley catheters, which are equipped with an inflatable balloon at the tip and are used for urine incontinence, terminal patients, and bladder drainage following surgery or an incapacitating injury or illness.
Infusion catheters are used for therapeutic introduction of a fluid, such as saline solution, into a body cavity or a vessel. In contrast to injection, infusion catheters allow for the introduction of a larger volume of a less concentrated solution over a more prolonged period of time.
Different catheter tips or guide devices may be used to guide a catheter to a target site within a patient's body. Often the target site is buried within a soft tissue, such as a brain or liver, and can be reached only by a convoluted pass through small vessels or ducts in the tissue. The difficulty in accessing such regions is that the catheter must be flexible in order to follow the convoluted pass into the tissue and at the same time stiff enough to allow the distal end of the catheter to be manipulated from an external access site.
Two general methods for the introduction of catheters have been commonly used. The first method employs a highly flexible catheter having a dilated distal end. A major limitation of this method is that the catheter will only travel in the path of highest blood flow rate, and therefore, many target sites with low blood flow rates cannot be accessed. Another limitation is that the dilated distal end makes it difficult to introduce the catheter through very small vessels or ducts without causing damage to the surrounding tissue.
In the second prior art method, a flexible guide wire having a distal bend is guided by alternatively rotating and advancing the wire to the target site. With the wire in place, a thin-walled catheter is then advanced along the wire until the distal catheter end is positioned at the target site. Once the catheter is advanced, the guide wire may be withdrawn to allow fluid delivery or withdrawal through the catheter. However, one of the disadvantages of this prior art method is that it is often very difficult to accurately position the catheter in a desired location within the patient's body, as the guide wire will often move away from the target site during the insertion of the catheter. Yet another limitation is that, because of the linear translation and/or rotational forces exerted upon the catheter during its insertion, translation and/or removal from its intended location, the guide wire may migrate from its original location and/or back out of the operative site altogether through the lumen of the catheter.
There have been some attempts to overcome the problems of know guide wire devices. For example, U.S. Pat. No. 5,167,239 to Cohen et al. describes an anchorable guidewire for use in various medical applications having an elongate guidewire body with an inflatable anchoring member or balloon and a deactuatable check valve positioned on the body for maintaining inflation of the balloon. The balloon is inflated via a syringe connected to a hub on the guidewire body.
However, the guide wire disclosed in Cohen et al. still suffers from a number of disadvantages and shortcomings. One of the most significant problems is that the guide wire of Cohen et al. may still migrate from the desired location during the insertion of the catheter. This is because the only securing mechanism holding the guide wire of Cohen et al. in place is the contact between the inflated balloon and surrounding cavity walls. The balloon described in Cohen et al. has a smooth surface, thereby making it prone to slippage during the insertion process, especially due to linear and/or rotational forces exerted upon the guide wire during the insertion of the catheter.
Another problem with the guide wire device disclosed in Cohen et al. is that it is rather complex and bulky, which makes it unsuitable for use in bodily cavities having a very small diameter. Additionally, the device of Cohen et al. is constructed with expensive materials, and therefore has to be reused multiple times, which requires complex sterilization procedures.
Yet another deficiency of the guide wire of Cohen et al. is that it is not able to be positioned as optimally as may be desired. For example, the guide wire of Cohen et al. does not provide a direct visual feedback of the area ahead, behind, and around the guide wire to optimize positioning of the guide wire. Further, the guide wire does not include material for externally identifying its position, such as a radio-opaque material. Therefore, one is not able to easily identify the position of the balloon via an external imaging modality, such as radiographic or ultrasonic imaging. Each of these shortcomings contributes to one's inability to position the guide wire as precisely as may be desired.
A further deficiency of the guide wire of Cohen et al. is that it lacks the capability to precisely gauge the size of the environment in which it is being used to provide physiological measurements and feedback that could aid precise and secure positioning of the guide wire. For example, there is no way for the surgeon to know the intra-lumen diameter of the bodily cavity in which the guide wire is to be secured, and no way to accurately adjust for changes in this diameter as the guide wire is moved within the cavity. Because it has no mechanism for measuring the intra-lumen diameter at different points within the cavity, one is not able to properly adjust the amount of pressure supplied to the anchoring balloon and thereby prevent slippage or migration of the balloon.
What is desired, therefore, is an improved guide wire device that addresses the dislocation, migration and instability problems of known guide wire devices. What is also desired is a guide wire that allows for more precise and minimally traumatic introduction, translation and/or removal of a catheter, instrument, device, implant or the like into, through, and out of the body.